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The ISLAnds Project. III. Variable stars in six Andromeda dwarf spheroidal galaxies

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Martinez-Vazquez, CE, Monelli, M, Bernard, EJ, Gallart, C, Stetson, PB, Skillman, ED, Bono, G, Cassisi, S, Fiorentino, G, McQuinn, KBW, Cole, AA ORCID: 0000-0003-0303-3855, McConnachie, AW, Martin, NF, Dolphin, AE, Boylan-Kolchin, M, Aparicio, A, Hidalgo, SL and Weisz, DR 2017 , 'The ISLAnds Project. III. Variable stars in six Andromeda dwarf spheroidal galaxies' , Astrophysical Journal, vol. 850, no. 2 , pp. 1-26 , doi: 10.3847/1538-4357/aa9381.

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Abstract

We present a census of variable stars in six M31 dwarf spheroidal satellites observed with the Hubble Space Telescope. We detect 870 RR Lyrae (RRL) stars in the fields of And I (296), II (251), III (111), XV (117), XVI (8), and XXVIII (87). We also detect a total of 15 Anomalous Cepheids, three eclipsing binaries, and seven field RRL stars compatible with being members of the M31 halo or the Giant Stellar Stream. We derive robust and homogeneous distances to the six galaxies using different methods based on the properties of the RRL stars. Working with the up-to-date set of Period-Wesenheit (I, B–I) relations published by Marconi et al., we obtain distance moduli of μ 0 = [24.49, 24.16, 24.36, 24.42, 23.70, 24.43] mag (respectively), with systematic uncertainties of 0.08 mag and statistical uncertainties <0.11 mag. We have considered an enlarged sample of 16 M31 satellites with published variability studies, and compared their pulsational observables (e.g., periods and amplitudes) with those of 15 Milky Way satellites for which similar data are available. The properties of the (strictly old) RRL in both satellite systems do not show any significant difference. In particular, we found a strikingly similar correlation between the mean period distribution of the fundamental RRL pulsators (RRab) and the mean metallicities of the galaxies. This indicates that the old RRL progenitors were similar at the early stage in the two environments, suggesting very similar characteristics for the earliest stages of evolution of both satellite systems.

Item Type: Article
Authors/Creators:Martinez-Vazquez, CE and Monelli, M and Bernard, EJ and Gallart, C and Stetson, PB and Skillman, ED and Bono, G and Cassisi, S and Fiorentino, G and McQuinn, KBW and Cole, AA and McConnachie, AW and Martin, NF and Dolphin, AE and Boylan-Kolchin, M and Aparicio, A and Hidalgo, SL and Weisz, DR
Keywords: galaxies: dwarf, galaxies: stellar content, stars: variable
Journal or Publication Title: Astrophysical Journal
Publisher: Univ Chicago Press
ISSN: 0004-637X
DOI / ID Number: 10.3847/1538-4357/aa9381
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Copyright 2017 The American Astronomical Society

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